Min gas calculation: + or - 500 PSI?

[HenrikBP]

I'm doing minimum gas calculations for a 100' dive using an AL100 tank. 2 divers figuring SCR of 1 ft3/min per diver.

I get minimum gas 40 ft3 which in the AL100 (100 ft3 at 3300 PSI => tank factor 0.03 ft3/PSI or 3 ft3/100 PSI) works out to 1333 PSI, which is then rounded up to 1400 PSI.

So do I add 500 PSI to the 1400 PSI? As in "be back on the boat with 500 PSI". Or do I figure, if no gas sharing takes place I'm well within "boat standards", and if gas sharing takes place we're just happy that we made it home safe and don't care about the 500 PSI?

Really basic, I know. But we all start somewhere. And yes, we did cover min gas during Fundies, but my notes are fuzzy on the 500 PSI.

Thanks,

Henrik

 

[lamont]

rock bottom replaces the 500 psi rule, so pretty much just ignore that...

if you're following rock bottom rules you should be back with 500 psi...

you can use the 500 psi rule to determine when you should finally surface at the very end of a dive...

 

[HenrikBP]

Great - thanks Lamont.

Henrik